I just found out about this. There are four double coming up at DuMouchelles in Detriot, MI.

There are three 28 gauges: a Westely Richards, Webley & Scott and an FT Bakers. There’s also a 20 gauge Webley & Scott 700. These guns are all boxlocks with straight grips and double triggers
All I know about the guns is in the auctioneer’s listing. To see them, go to this page. Click on the March 12 auction. The guns are lots 49-52.